1. Field of the Invention
The present invention relates to a method and apparatus for servicing well casing and the like and more particularly to such a method and apparatus which are particularly well suited to cleaning, as may be employed in a particular well, the interior surface of the well casing, the well casing perforations, the liner slots, the wire wrap just outside the liner slots and, to some extent, the face of the formation substantially more effectively than has heretofore been possible with conventional methods and apparatus and at substantially less expense and with significantly more reliability. 2 Description of the Prior Art
The continued operation of wells of all types requires that the well structure and, to some extent at least, the fluid bearing formation beyond the well structure be cleaned or otherwise treated to insure a substantially unobstructed path for fluid flow from the fluid bearing formation into the interior of the well casing. A variety of devices and methods have in the past been employed for this purpose and they have operated with some success. However, these are notable drawbacks with the operation of such prior art equipment.
When cleaning well casing, it has been found in the past that the application of a treating fluid first through high pressure jets followed by the application of the treating fluid under pressure in the manner of a pressurized wash or bath works best. Thus) tools known in the trade as jet washing tools and opposed cup pressure washing tools are known for use in performing these two separate functions. However, there has in the past been no way to use the tools in conjunction without removing the jet washing tool from the borehole and then attaching and inserting the opposed cup pressure washing tool into the borehole for the performance of its cleaning operation. The need to remove one piece of equipment from the borehole before inserting and using the second piece of equipment is extremely time consuming and, of course, therefore expensive. The additional handling required also increases the possibility of damage to the equipment and injury to personnel. Furthermore, the enormous amount of time required may cause the steps to be performed with less precision than would be desired or in less than the optimum time of application.
There are other problems associated with the use of conventional equipment. It has been known to operate well equipment of a variety of types by rotation of the well tubing on which the equipment is mounted within the well casing. Thus, where a particular piece of equipment during use in the well requires adjustment such as to place it in a different mode of operation, the typical procedure for doing so is to pivot entire string of well tubing on which the equipment is mounted to achieve the result desired in the equipment. Similarly, conventional jet washing tools must be rotated in the casing in order to insure that all of the surfaces of the well casing and the perforations thereof are subjected to the high pressure spray. Since the area to be cleaned is many times the length of the tool, such rotating must be performed a multiplicity of times before the jet washing operation is completed.
Such rotation of the well tubing requires the use of a rotational power source at the earth's surface which is expensive and time consuming to set up and use. Furthermore, since boreholes commonly are deviated from true vertical, sometimes to substantial degrees, throughout their lengths, rotation of the well tubing causes wearing of the tubing and tools and the well casing in the points of contact resulting from such deviation.
Therefore, it has long been appreciated that it would be desirable to have a method and apparatus for servicing well casing and the like which permits the use of a pair of tools in the well casing in sequence without having to remove the well tubing from the borehole between the application of the first tool and the second tool; which permits operation of a tool at depth in a borehole without requiring rotation of the well tubing; which permits the application of jet washing spray to the well casing in a much more effective and efficient manner than has heretofore been possible; which achieves the optimum synergistic effect in the application of jet washing and opposed cup pressure washing; and which substantially reduces the time and expense associated with the servicing of well casing and the like.